How much of a hero is Lancelot in Sir Thomas Malory's Le Morte d'Arthur?

Depictions of Sir Lancelot, including Sir Thomas Malory’s 1485 version of the tales of Arthur and the Round Table, invariably portray him as among the bravest, most loyal and most resourceful of all the knights of the Round Table. In fact, in Malory’s Le Morte d’Arthur, Lancelot (also spelled Launcelot), is identified in Book II, Chapter VIII as one of the two greatest knights in the world, along with Sir Tristram (or Tristan or Tristam). In the following passage from that chapter, court wizard and counsel Merlin prophesies that those two knights should do battle:

“THE meanwhile as this was a-doing, in came Merlin to King Mark, and seeing all his doing, said, Here shall be in this same place the greatest battle betwixt two knights that was or ever shall be, and the truest lovers, and yet none ,of them shall slay other. And there Merlin wrote their names upon the tomb with letters of gold that should fight in that place, whose names were Launcelot de Lake, and Tristram.”

“Then Merlin laughed. Why laugh ye ? said the knight. This is the cause, said Merlin : there shall never man handle this sword but the best knight of the world, and that shall be Sir Launcelot or else Galahad his son, and Launcelot with this sword shall slay the man that in the world he loved best, that shall be Sir Gawaine.”

References to or depictions of Lancelot’s bravery and heroism abound throughout Malory’s story. In Book VI, Chapter XI, for instance, the brave knight saves a village from two giants, “well armed all save the heads, with two horrible clubs in their hands.” As Malory describes the confrontation,

“Sir Launcelot put his shield afore him and put the stroke away of the one giant . . . When his fellow saw that, he ran away as he were wood . . . and Launcelot after him with all his might, and smote him on the shoulder, and clave him to the navel. Then Sir Launcelot went into the hall, and there came afore him three score ladies and damosels, and all kneeled unto him, and thanked God and him for their deliverance.”

Malory devotes a considerable portion of Le Morte d'Arthur to Lancelot. In addition to the search for the Holy Grail, Malory devotes an entire book to Lancelot and Guinevere’s affair, and, in Book XI, describes the knight’s travels and ensuing acts of heroism, including rescuing “the fairest lady” from and unjust imprisonment and soon after slaying a serpent. If Sir Lancelot is brave and resourceful, however, he is also ultimately the instrument of King Arthur’s doom. Lancelot’s affair with Queen Guinevere, while known to Arthur, has the effect of undermining the integrity of the royal court and leads ultimately to both the king’s death and to the demise of the Round Table, at which Lancelot had once participated in good standing. Not even Sir Lancelot’s bravery in pursuit of the Holy Grail and his enduring loyalty to Arthur can compensate for the weakening of the king’s position by virtue of his palace intrigue involving Guinevere.